How Do You Send a Large 4K PNG Without Email Bounce?

Do not email the master. A native 3840x2160 PNG from this archive is usually 3 to 18 MB, and a pair of them plus a PSD will cross the limit that actually exists on the receiving server, not the limit Gmail advertises. Send a 200 to 400 KB preview in the message. Put the PNG on a transfer host the client's IT already allows. Write the expiry in the subject line.

The hand-off page is what goes in the folder. This page is why the folder does not travel as an attachment.

How large the file really is, and who will bounce it

Uncompressed 8-bit RGB at 3840x2160 is 24,883,200 bytes. PNG DEFLATE brings that down. A gradient plate may sit near 2 to 5 MB. A dense HUD or glitch plate can sit at 10 to 18 MB. Two plates are already a 20 MB conversation. Outlook on the other side may be set to 10 MB. That is the bounce: 552 5.2.3 or a polite "message too large" that lands after you have left the office.

Common ceilings, treated as rumors you must confirm:

• Gmail: 25 MB for the whole MIME message, not for one file. Base64 makes a 18 MB PNG look like about 24 MB on the wire. One busy plate can fail even when "Gmail allows 25."
• Many Microsoft 365 tenants: 10, 20 or 25 MB, set by their admin, not by you.
• Government and bank relays: 5 or 10 MB, plus a block on file-host links. Ask before you send.
• Slack free workspaces: 1 GB storage but a per-file limit that is not a master archive. Fine for a preview. Poor as a DAM.

Zip will not save you. PNG is already compressed. plate.png at 14.1 MB becomes plate.zip at 14.0 MB and still bounces. Zip is a wrapper so preview, original and readme travel together on a host that accepts the size. It is not a shrink ray.

What you may email:

• 01_preview/slug-1920.jpg at 150 to 400 KB.
• The URL to the transfer.
• The SHA-256 of the master, if you are being careful.
• A one-line reminder: "Place the PNG in 02_original. Do not place this JPEG."

What you may not email: the 3840x2160 PNG, a Photoshop file that embeds it, or a "quick export" that is secretly still 12 MB.

If you only have email and the receiver blocks hosts, ask them for an inbound SharePoint library or an SFTP. That request is a production task, not a personal failure. Put the three numbers in the ticket: file type PNG, pixel size 3840x2160, bytes on disk. IT can then raise a limit or open a path.

Which pipe to pick, and how not to lose the file

Prefer the client's house. If they live in Microsoft 365, upload to their SharePoint and @-mention them. If they live in Google, use their Drive, not your personal one. Access control already exists. When the designer leaves your studio, the file is still in the client's tenancy.

If there is no house:

• Dropbox or Drive link, domain-restricted when the deck is confidential. "Anyone with the link" is for public campaign assets, not for unreleased product UI.
• WeTransfer or a similar one-shot, paid if you need a longer expiry. Put expires: 2026-08-24 in the email and in your calendar. When it dies, you still have client-out/ locally.
• SFTP or a signed HTTPS URL from the client's CDN team, for shops that will not touch consumer hosts.

Name the upload the same as the disk file: slug-3840x2160-srgb.png. A link titled IMG_8841.png will be misplaced in a week.

Do not upload the site's 1920 preview and call it the transfer. People will place it. Start from the master you verified.

If you must squeeze a review through email only, export a 1920 JPEG at quality 75 and say, in the first sentence, that the master follows on the host they named. Never downsample the only copy. The library master stays 3840x2160.

Motion is a different pipe. A 4K loop from Unique Live Wallpaper can be hundreds of megabytes. Do not attach it. Do not rename it to sit next to the PNG in the same zip unless the client asked for both and the host can take the size.

After they confirm, snapshot the folder. Transfer links rot. Mailboxes get legal-holds that still cannot find a 14 MB PNG that never arrived. Your catalog is the copy that still exists in December.